This invention relates to vegetation cutters and has more particular reference to lawnmowers of the rotary type that are, in use, supported upon a cushion of air.
It is known to provide an air-cushion supported vegetation cutter in which an impeller for generating the air cushion, the cutter, and the armature are mounted on a common shaft. In an arrangement of this kind it has been proposed to provide a cooling air flow over the motor to prevent the motor overheating. Such a cooling air flow may be provided by a separate motor fan but if the fan is to provide all of the cooling air flow it must be quite bulky due to its relatively slow speed. Thus relying upon a separate motor fan to provide all the flow of motor cooling air is not entirely satisfactory.
It has been proposed to provide a cooling arrangement in which the impeller that generates the air cushion also provides all the cooling air flow over the motor and thus the disadvantages of providing a separate motor fan are overcome. In this proposed arrangement, however, the cooling air flow for the motor is kept apart from the other intake of air flow on the inlet side of the impeller and the two air flows do not combine until they are acted upon by the impeller; the impeller therefore has to provide all the power for the motor cooling air flow.